This application requests support for a Keystone Symposia meeting entitled Th17 Cells in Health and Disease, organized by Chen Dong, Vijay K. Kuchroo, Jay K. Kolls and Brigitta Stockinger, which will be held in Keystone, Colorado from February 5 - 10, 2012. Nearly 5 years ago, a new type of T cell, called the Th17 cell, was discovered. Th17 cells have unique regulation and have been shown to be associated with many types of immune diseases and cancer. Since the first Keystone Symposia meeting on Th17 cells in 2009, there has been rapid progress in our understanding of the roles of IL-17-producing T cells in innate immunity to infection, the plasticity of Th17 cells, and genetic diseases associated with Th17 defects. This second Keystone Symposia meeting, entitled Th17 Cells in Health and Disease, will be the only one of its type in 2010-2012. The goal of this meeting is to gather experts in basic and clinical research areas and provide a productively interactive forum to further our understanding of Th17 regulation and function in immune responses and diseases. Opportunities for interdisciplinary interactions will be significantly enhanced by the concurrent meeting on The Biology of Cytokines, which will share a keynote address and two plenary sessions with this meeting. PUBLIC HEALTH RELEVANCE: Th17 cells are a new lineage of T cells, cells belonging to a group of white blood cells known as lymphocytes, which play beneficial roles in mucosal immunity but are also associated with many types of immune diseases and cancer. Recently, there has been an explosion in our understanding of these cells in disease that give the scientific community unprecedented insight into the role of Th17 cells in human immunity. The 2012 Keystone Symposia meeting on Th17 Cells in Health and Disease will gather experts in basic and clinical research areas and provide an interactive forum to further our understanding on Th17 regulation and function in immune responses and diseases.